Method for purifying aromatic compounds



United States Patent 3,087,969 METHOD FOR PURIFYING AROMATIC COMPOUNDS Alexander H. Widiger, Jr., Midland, Micl1., assignor to 3,087,969 Patented Apr. 30, 1963 uum distillation and the like. Good results have been obtained when the crude synthetic phenol is treated with an aqueous caustic solution at a temperature of from about 60 to 120 C. and air or other oxygen-containingh D l h. 5 gas is blown through at between about 20 and about 100 g z g gggss g Mldland Mm a cor p.s.1., to provide from about 0.05 to 2 cubic feet of oxygen No Drawing. Filed Mar. 29, 1961, Ser. No. 99,024 P Pound of the Phenol 8 Clai (01, 260-620) Some of the phenols which can be purified in accord ance with the present invention are o-phenylphenol, p-

The present invention relates to a new and useful 10 phenylphenol, p-sec.-butylphenol, p-tert.-butylphenol, pmethod for purifying aromatic compounds and is more cresol, o-cresol, di-t.-butylphenol, phenol and the like, preparticularly concerned with a new method for purifying pared by the reaction of the corresponding chloroaryl aromatic compounds synthetically prepared having the compound with sodium hydroxide. following generic formula: The alkaline conditions conveniently can be obtained be employing substantially any water-soluble alkali, par- OH ticularly sodium hydroxide. Other alkalies which can be R employed are, for example, potassium hydroxide, sodium carbonate, potassium carbonate, and the like. The concentration of the alkali in the reaction mixture is from 0.1 to about 2 percent by weight of the crude phenol.

wherein R re resents lower alk l, hen l or alk l hen l and R repre ents hydrogen or lo wer Zlkyl. 'l hi s cla s s T Oxygen contammg gas 15 alrihowever of compounds will hereinafter be referred to as phenols. It Is to be linilerstood that pure Oxygen or any other In the manufacture of phenols wherein the phenolic hyoxygen contiunmg gas be employed find that the rate .droxyl is introduced by the caustic hydrolysis of aryl chlo- 2 g i fi f z i g g tahdlusted to Supply ride, a number of impurities carry over with the desired g e 1 e or h product. Various methods have been proposed to reeflfonowmg Exampes are mustrauv? 9 t 6 present m these substances Since they disc 01 or the phenol invention but are not to be construed as limiting. pfioducit especlially crivhendthe produtgtl is in1 tlilet sal(t1 form as EXAMPLE 1 t eso ium sa t, an ren er it unsta eto 1g an stora e.

Some of the proposed methods have stabilized the pl ie- 16500 q of crude ortho'phenylpheiloli prFpared Hols Sufiicienfly to be used commercially However none by the caustlc-chlorobenzene process, Was mixed with 120 have completely removed the impurities. Repeated and l of a caustl'c E 1,500 pounds of E laborious purification steps are necessary to obtain the tmg mlxture, was to between 95 and 1 phenolin a Stable fomL one of the more common meth C. and 45.6 cubic feet of arr per mmute (calculated at ods, crystallization, is expensive to employ commercially standampressure. and temperature) was pissed through on a large scale. Therefore, it would be desirable to prothe Solution fight hours Pressur? m the Teactor Vida an imxpensive method to purify phenols; Was lO-SO p.s.1.g. Upon completion of thls operation the It is an object of the present invention to provide a reaction mixture was fractlonally distilled under reduced novel process for the purification of the synthetic phenols 40 pressure to obtam ig i fi produced by the caustic hydrolysis of arylchlorides which lflol P as ed 3 f P f 8 yield a product stable to discoloration from light or storreezmg pomt 0 7 a 01 5 3 0 f d age. A further object of the present invention is the proat 25 i f tamed was to vision of a method for the purification of the desired prodbe supenor In Color and hght Stablhty, as compared g l uct which process is of a less corrosive nature than the a m of orthoiphepylphenol whl'ch was not oxldlzed present day methods. These and other objects will bebut pun ed by dlsmlanon' come apparent to those skilled in the art from the fol- EXAMPLES lowing specification and claims.

It has now been found that a synthetic phenol one stage A crude Q P P epal'ed by the caustlc'chlorobfmzene of which is derived in the arylchloride caustic process, P Q contalmng from to Percent by Welght of can be purified by the alkaline oxidation of the crude prodalkfh and from 57 to Percent Watel: was heated net. The process reduces the impurities of which little 90 llPdef pressufe- Dunng i118 g. b is known as to their identity, to tar-like residues which can troduced m f manner bl'lbble through the reactlon be separated from the phenol thereby to produce a light- 'f The was mamtamed at 40 to 50 P Squat? stable, color-stable product of high chemical purity. The Inch, gauge, and regulated to Introduce about cublc separation of the phenol can be accomplished readily and HP hour, P Pound of p The Ieafitlon Was conveniently from the tars and other impurities by vaccontinued for 6 hours.

Table 1 sin fi g h t i I Results of days exposed expressed grams Amt. as color ehan go in Na salt EX.N0. Compound Method 1120, Top Maul Resldue ml. Load, cut out S. Crude NaOH grams gms gm gms. Percent Days Color 4 3. 25 194 34.0 135.5 23.3 12 11 L. ellow.

' 8 1 134.8 0 0 104.8 7.5 90.5 4.2 4 11 L. green.

p-Cresol O 300 3.0 25 302.5 41.1 241.1 19.5 6.4 12 V. 51. yellow.

---------- G 0 .2 at. s at a2 a area .2 3. i 8 323.0 0 0 253.0 32.8 211.8 7.8 3.1 46 V. dk. yellow.

1 O-oxidized, Ceontrol.

3 EXAMPLES 9-13 In the manner of Examples 2-8 various of the phenols made 'by the chlorobenzene process were purified. The purified phenols were subjected to a color stability test. The results of the operations are set forth in the following table.

cient to provide from about 0.05 to about 2 cubic feet of oxygen per pound of phenol and at a pressure from 20 to 100 pounds per square inch.

3. A method for purifying ortho-phenylphenol to remove the color forming impurities produced in the manufacture of the phenol by the caustic hydrolysis of chloro- T able II Still Result 01 days exposed expressed Compound, of free as color changing EX. Weight in Amt. v phenol No. Compound Method grams Hi Top Main Residue ml. Load, cut, out, grams gms. gms. Crude NaOH gins. Percent Days Color 0 436 3 0 25 309.2 22 129. 157 50. 7 42 Orange. C 302. 4 0 0 302. 4 24. 7 241. 1 35. 5 11. 7 42 S1. dk. orange. 0 228.6 2 O 228.0 30. 8 166.9 30.3 13.2 38 White. 0 154.6 0 0 154.6 16. 6 122.0 14. 6 9. 45 38 Straw.

1 O- oxidized, O control.

This application is a continuation-in-part of my copending application, Serial No. 796,272, filed March 2, 1959, and now abandoned.

-I claim:

1. A method for removing the color forming impurities from nuclear substituted phenols prepared by the caustic hydrolysis of arylchloride which comprises treating the crude phenol having the formula wherein R represents a member selected from the group consisting of lower alkyl radicals having from 1 to 4 carbon atoms, phenyl and alkyl phenyl and R represents a member selected from the group consisting of hydrogen and lower alkyl radicals, with an oxygen-containing gas in an amount to provide from 0.05 to about 2 cubic feet of oxygen per pound of phenol and at a temperature of from about 60 to about 120 C., in the presence of an aqueous solution of from about 0.1 to 2 percent by Weight based on the phenol of an alkali selected from the group consisting of carbonates and hydroxides of alkali metals.

2. A method as set forth in claim 1 wherein the oxygencontaining gas is air and is supplied in an amount sufiibenzene which comprises treating the impure orthophenylphenol with an oxygen-containing gas in an amount sulficient to provide from 0.05 to about 2 cubic feet of oxygen per pound of phenol at a temperature of about to C. in the presence of an aqueous solution of from 0.1 to 2 percent by weight based on the phenol of the phenol of an alkali selected from the group consisting of hydroxides and carbonates of the alkali metals.

4. The method of claim 1 wherein said phenol is p-secbutylphenol.

5. The method of claim 1 wherein said phenol is pcresol.

6. The method of claim 1 wherein said phenol is p-t.- butylphenol.

7. The method of claim 1 wherein said phenol is di-t.- butylphenol.

8. The method of claim 1 wherein said phenol is phenylphenol.

References Cited in the file of this patent UNITED STATES PATENTS 2,394,652 Alves et al. Feb. 9, 1946 2,829,176 Clough Apr. 1, 1958 2,885,444 Fookes et al. May 5, 1959 FOREIGN PATENTS 619,856 Great Britain Mar. 19, 1949 

1. A METHOD FOR REMOVING THE COLOR FORMING IMPURITIES FROM NUCLEAR SUBSTITUTED PHENOLS PREPARED BY THE CAUSTIC HYDROLYSIS OF ARYLCHLORIDE WHICH COMPRISES TREATING THE CRUDE PHENOL HAVING THE FORMULA 